Christmas Cactus

My Christmas Cactus is already blooming. I've had my Cactus in the same south window for as long as I've had it (7 yrs). It grows fine during the summer because I have mini blinds to block out the hot sun. I have two questions actually: 1. Why is it blooming so early and will it bloom again for Christmas? and 2. How or what can I do to make it bloom later? I usually have blooming at Christmas time.